Environmental Health Perspectives Vol. 27, pp. 309-316, 1978 Landfill Disposal Systems by Karen M. Slimak* The current status of landfil disposal of hazardous wastes in the United States is indicated by present- ing descriptions of six operating landfills. These landfills illustrate the variety of techniques that exist in landfill disposal of hazardous wastes. Although some landfills more effectively isolate hazardous waste than others, all landfills must deal with the following problems. Leachate from hazardous waste landfflls is generally highly polluted. Most landfills attempt to contain leachate at the site and prevent its discharge to surface or groundwaters. To retain leachate within a disposal area, subsurface barriers of materials such as concrete, asphalt, butyl rubber, vinyl, and clay are used. It is difficult to assure that these materials can seal a landfill indefritely. When a subsurface barrier fails, the leachate enters the ground- water in a concentrated, narrow band which may bypass monitoring wells. Once a subsurface barrier has failed, repairs are time-consuming and costly, since the waste above the repair site may have to be removed. The central problem in landfill disposal is leachate control. Recent emphasis has been on developing subsurface barriers to contain the wastes and any leachate. Future emphasis should also be on techniques for removing water from hazardous wastes before they are placed in landfills, and on methods for preventing contact of the wastes with water during and after disposal operations. When leachate is eliminated, the problems of monitoring, and subsurface barrier failure and repair can be addressed, and a waste can be effectively isolated. A surface seal landfill design is recommended for maintaining the dry state of solid hazardous wastes and for controlling leachate. Any impervious liner is utilized over the top of the landfill to prevent surface water from seeping into the waste. The surface barrier is also the site where monitoring and maintenance activities are focused. Barrier failure can be detected by visual inspections and any repairs can be made without disturbing the waste. The surface seal landfill does not employ a subsurface barrier. The surface seal landfill successfully addresses each of the four environmental problems listed above, provided that this landfill design is utilized for dry wastes only and is located at a site which provides protection from groundwater and temporary perched water tables. Introduction Although landfils are probably the most com- monly used and the oldest methods of hazardous waste disposal, until recently landfill disposal has received relatively little study. Largely because of an increased awareness of environmental effects of anthropogenic activities and the occurrence in the past decade of several hundred damage incidents related to disposal of hazardous wastes (1), there has been an increased interest in identifying sources of hazardous wastes, learning what present disposal practices are, and assessing the adequacy of these procedures. The largest portion of such studies has been sponsored by EPA's Office of Solid Wastes through its general study of reduction, treatment, * Environmental Engineering Division, TRW Inc., 800 Follin Lane, S. E., Vienna, Virginia 22180. Present address: J R B As- sociates, Inc., 8400 West Park Drive, McLean, Virginia 22101. and disposal of approximately 600 hazardous wastes (2) and through assessments of hazardous waste generation and disposal in 13 industrial categories. Generally, as more has become known about the need for isolation of hazardous wastes, landfill disposal procedures have been developed to provide for increased waste isolation. Considerable variety still exists, however, among types of land- fills used (and the extent of waste isolation achieved) for hazardous waste disposal. This paper summarizes the current status of landfill disposal of hazardous wastes in the United States. The general types of landfils will be defined and will be illustrated by descriptions of several operating hazardous waste landfills. The advan- tages, disadvantages, and problems of each landfill will be discussed. The paper will conclude by sum- marizing the environmental problems associated with landfill disposal of hazardous wastes and in- troducing a suggested landfil system which may solve some of these environmental problems. December 1978 309
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